-
Anterior pituatary gland releases entirely...
different set of hormones
-
set of hormones functions that are released by anterior pituatary gland...(3)
-involved in organizational(developmental) and activational aspects of sexual behavior
-releases hormones involved in the body's response to stress
-also releases hormones involved in growth
-
Anterior pituitary gland release is casued by hormones...
released withing the hypothalamus that flow down to the anterior pituitary
-
(Steps to anterior pituatary gland) 1-2
1. hypothalamic hormones are released into a capillary netwrk.
2. these hormones travel down through portal vein in pituatry stalk. hormones either excite or inhibit other hormones of anterior pituatry to be relasesd into bloodstream
-
(anterior pituatry gland) Hypothalamic hormones that act on the anterior pituatry are called...
- releasing factors
- *it makes the anterior pituatary gland to release hormones.
-
(example of releasing factors) Thyrotropin-releasing hormone (2)
1. released by hypothalamus travels to the anteiror pit. where it promotes release of thyrotropin
2. Thyrotropin reaches the thymus gland and causes it to release other hormones into the general blood stream, which acts on ither organs to sitmulate metabolism
-
(sexual behavior releasing factors) Gonadotropin-releasing hormone (GRH)
- 1.causes the anterior pit. to release gonadotropin hormones
- *follicle-stimulating hormone
- *luteinizing hormone
^these hormones act on the gonads, to cause a release of hormones there
-
Gonadotropins act on the gonads (2)
males= testes
females= ovaries
-
(gonads) Gonads release the same steroid hormones
-androgens (testosterone)
-estrogens (estradiol)
- *both male and females gonads release these hormones but
- males: androgens> estrogens
- females: estrogens> androgens
-
-
-
3 mechanisms for regulation (increase or decrease( of hormone release
-neural
-hormonal
-non-hormonal chemicals
-
(mechanisms for regulation) Neural (3)
-all glands except anterior pit. are affected by neural inputs
-pineal and post. pit. glands receive inputs form areas in the brain
-other glands receive inputs from the autonomic (peripheral) nervous system
-
(mechanisms for regulation) Hormonal (2)
- -provides feedback
- *ex) high levels of androgens reeased by testes could be sensed by brain to shut off further release of gonadotropin-releasing hormone
-small testicles in males taking artificial androgens
-
(mechanisms for regulation) Non-hormonal chemicals
-glucose (sugar) can cause the release of the hormone insulin from the pancreas
-
-
- *all begin with primordial gonad
- **it can go into testes or ovaries
-
Each primordial gonad is made up of..
-medulla and cortex
medulla: potential to develop into testis
cortex: into an ovary
-
What decided which way the gonad will go?
- 6 weeks post conception, Y chrom. causes production of Sry protein
- *causes medulla of primordial gonad to turn into testes
-
If Sry protein injected into a developing XX female,
person will develop testes
-
If Sry protein is blocked in XY male,
person will develop ovaries
-
6 weeks post-conception, we have 3 sets of reprductive ducts
-wolffian system
-mullerian system
-
(reproductive ducts) Wolffian system
- can fevelop into male ducts
- *seminal vesicles and vas deferens
-
(reproductive ducts) Mullerian system
- can develop into female ducts
- *uterus and fallopian tubes
-
3 months post-conception,
testes begin to secrete the hormones testosterone and mullerian-inhibiting susbtance
-
If testes develop from primordial gonads and begin relaesing testostorone and mullerian-inhibitng substance then...
male internal reproductive structures will develop
-
-
W/o active testes
- Mullerian system will develop on its own and the wolffian system will not develop
- *ovaries are not active during development
-
In experiment of adult female and male rats and the cycle of gonadotropin release
-adult females have a cyclical pattern of gonadotropin release
-adult males have a steady release of gonadotropins
-
Hormones released from the gonads affect..
the development of the brain
-
The differentation between male and females hypothalamus occurs around..
time of birth
-
What two hormones masculinzes the brain?
- testosterone and estradiol
- *especially estradiol
**testosterone can be easily converted into estradiol by aromatase
-
Evidence of estradiol masculinazing our hypothalamus (3)
-injectons of estradiol can masculanize the hypothalamus
- -dihydrotestosterone fails to masculinize the hypothalamus
- *an androgen that cannot be cnoverted into estradiol
-agents that block the conversion of testosterone to estradiol block the masculinization of the hypothalamus
-
how do females not have masculinized brains? (2)
-ovaries secrete almost no estradiol during development
- -around time of birth, we have a factor circuating our blood called alpha-fetoprotein
- *it binds to estradiol and prevents it from reaching the brain
-
how do males have estradiol around the brain but not females?
- - alpha fetoprotein cannot cross the blood-brain barrier
- *its actions are strictly on peripheral
- -alpha fetoprotein binds estrogen not testosterone
- *testosterone can get past this, and cross blood-brain barrier and reach the brain.
-
The perinatal effects of hormones are..
critical for future physiological characteristics of males and females as well as future sexual behavior
*however tehre is a long delay until they are sexually active
-
Steroid hormones released by gonads also ahve...
activational effects
***release of hormones in mature animals can directly lead to changes in sexual behavioer
-
Castration effects
- -leads to reduction and most often a cessation of sex behavior
- *presumed to be a result of loss of testosterone
**testostorone injections cna restore sexual behaviors
-
Does the amount of testostorone affect sex drive?
-sexual vigor does not seem to correlate with total amount of circulating testosterone
**when small amount of testostorne is added, it is sufficient to restore one's sexual life
-
IN males, steroid hormones appear to act on distinct regions of the brain...
medial preoptic area of the hypothalamus (mPOA)
-
Lesions on mPOA causes...
- abolished male copulatory behavior
- **andorgen implants here in castrated males restores copulation of males
-
mPOA neurons send their axons to...
motor-related regions of the brain which project to the spinal cord to produce motor sequences involved in male copulatory behavior
-
Female rats will only be receptive towards a male and his advances during..
- behavioral estrus
- *cyclical thign
-
ovariectomized females are not...
receptive to males at any time
-
A receptive female will act on a prescence of male by...
- lordosis
- *elevated rump
- *tail deflected one side
- ***easy access for the male rat
-
(female receptivity) without gonal steroid hormones...
no lordosis
-
Several brain regions critical for lordosis
-ventromedial nucleus of the hypothalamus (VMN)
-periaqueductal gray (PAG)
-medullary reticular formation
-
Estrogen and progestorone delivered directly to...
the VMN induce lordosis
- *lesions of VMN wipes out lordosis
- *electrrical stimulation of the VMN promotes lordosis
|
|
